Heat Pump Installation in a 300-Year-Old Property
At Option Energy Solutions, we thrive on a challenge—and this project was one of our most rewarding to date. We were tasked with designing and installing a low-temperature heating system in a 300-year-old property with wattle and daub construction. Combining heritage fabric with modern energy-efficient heat pump technology required careful planning, creative design, and true collaboration.
The Challenge: Heritage Meets Heat Geek
The property’s age and construction meant we couldn’t rely on standard U-value assumptions. We began with a Cardiff University study on wattle and daub wall performance to build a custom U-value model. From there, we used Heat Geek’s cutting-edge software and hardware to carry out a detailed room-by-room heat loss calculation.
One of our core aims was to reduce the design flow temperature as far as possible—settling on an impressive 43°C to optimise the efficiency of the planned system. From system layout to emitter sizing, every detail had to be engineered with precision to match the home’s unique needs.
Smart Layout, Smarter Solutions
To overcome restricted pipe routes, we relocated the domestic hot water cylinder and used 32mm MLCP pipework to bypass a major steel beam in the building. This let us maintain optimal flow rates while working around structural limitations.
The home’s heating demand was split into two distinct zones to reduce pressure loss and allow for better balancing. Wherever possible, we reused existing pipework to preserve the home’s layout while keeping installation disruption to a minimum.
Emitter Upgrades & Hydraulic Balancing
The original heating system simply wouldn’t have coped with the low flow temperatures of a heat pump. We replaced 11 of the 13 existing radiators with high-efficiency models from Stelrad and Milano, and installed all new IMI Calypso valves for precise balancing and easy commissioning.
With these changes in place, we were able to commission the system to run at a low weather compensation curve of 0.5—ensuring excellent efficiency without compromising comfort.
System Specification
The system is powered by a 12kW Vaillant Arotherm Plus air source heat pump, controlled via SensoComfort and SensoNet for full digital control and remote access. A fast-switching ESBE diverter valve with a 15-second actuator enables rapid mode changes between heating and hot water.
During commissioning in December and January, the system recorded Coefficients of Performance (COPs) above 4 and 5.5 respectively. With the customer on an off-peak tariff of just 7.5p/kWh, they were heating their home and hot water for as little as 1.36p per kilowatt-hour.
Customer Outcome: Low Bills, High Comfort
The end result? A comfortable 21°C throughout the home, low running costs, and a seamless integration of modern low-carbon heating technology into a heritage property.
This installation proves that, with the right planning and execution, heat pumps can be a brilliant solution even in the most unlikely properties.
Installed by Option Energy Solutions
Proudly serving West Sussex, Brighton, Surrey, and surrounding areas.
Specialists in air source heat pump design, installation, and commissioning.
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